JPH082116A - Reversible thermal recording medium and magnetic card - Google Patents

Abstract

PURPOSE:To enhance contrast by adding an org. low-molecular substance and a crosslinked resin matrix to a reversible thermal recording layer. CONSTITUTION:A reversible thermal recording medium 1 consists of a base material 2, the reversible thermal recording layer 3 provided on the single surface of the base material 2 and the color forming layer 4 provided on the other surface of the base material 2. The reversible thermal recording layer 3 is composed of a thermally crosslinked resin matrix containing an org. low- molecular substance. The resin matrix forms a layer holding the org. low- molecular substance in a uniformly dispersed state and largely exerts effect on the transparency of the recording layer at the time of transparency. Therefore, as the resin matrix, a mechanically stable resin high in transparency and excellent in film forming properties is pref. In order to enhance the heat- resistant strength of the recording layer, the reversible thermal recording layer 3 is thermally crosslinked. As the resin matrix used in the thermal recording layer 3, a thermoplastic resin, for example, a vinyl chloride type copolymer, an epoxy resin, a phenoxy resin or an acrylic resin or other thermosetting resin is designated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium capable of reversibly forming and erasing images reversibly by heating means such as a thermal head, and a magnetic card using the same.

[0002]

2. Description of the Related Art In recent years, with the spread of thermal heads, the demand for thermal recording media has expanded rapidly. Particularly in prepaid cards, which are rapidly becoming popular in the fields of communication, transportation, distribution, etc., magnetic information is often displayed on the card as visible information. Such magnetic cards are widely used as highway cards, prepaid cards for department stores, supermarkets, and JR Orange cards.

However, in such a recording medium, the area where the visible information can be displayed is limited, and for example, in the case of a high-priced prepaid card, the information may not be displayed when the balance is additionally recorded. In such a case, conventionally, a new card is reissued to deal with the problem, which causes a problem of high cost.

In order to solve such a problem, studies have been made on a reversible recording medium capable of repeatedly recording and erasing in the same area. When such a recording medium is used, old unnecessary information can be erased and new information can be displayed, so that it is no longer necessary to display the information and there is no need to reissue a new card. Further, by using such a recording medium as a facsimile sheet, for example, resources can be saved, which contributes to solving environmental problems.

Conventionally, as a heat-sensitive recording medium capable of reversibly recording and erasing such information, a high-grade material is used in a resin base material such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester and polyamide. Those having a heat-sensitive layer in which an organic low molecular weight substance such as alcohol or higher fatty acid is dispersed have been proposed (JP-A-54-119377, 5).
5-154198 and JP-A-2-1363).

The principle of forming and erasing an image on such a reversible thermosensitive recording medium lies in the difference in transparency of the thermosensitive layer when the temperature is raised to different temperatures and returned to room temperature. That is, such a recording medium shows a transparent state when it is heated to a predetermined temperature and returned to room temperature, and shows a cloudy state when it is heated to another temperature and returned to room temperature. A thermal head is used for recording on such a heat-sensitive recording layer, and a heat roll, a hot stamp, a thermal head or the like is used for erasing.

The white turbid state of the recording medium utilizes scattering of light, so that the hiding property is low and the contrast is poor. Therefore, there is a proposal to provide a metal reflective layer, a colored layer, or the like on the lower surface of the reversible thermosensitive recording layer.

[0008]

However, when a metal reflection layer is provided on the lower surface of the reversible thermosensitive recording layer, all the light transmitted through the transparent portion is reflected, and therefore, depending on the viewing angle, the light is generated by printing. It becomes difficult to check the cloudy parts.

When a colored layer such as black or blue is provided on the lower surface of the reversible thermosensitive recording layer, the amount of scattered light from the white turbid portion of the reversible thermosensitive recording layer is small and sufficient contrast cannot be obtained. It is necessary to thicken the reversible thermosensitive recording layer on the top. As a result, the energy required for recording increases, and when recording is repeated, early deterioration of the recording layer becomes remarkable.

Also, in order to improve the contrast of the cloudy part, a method has been proposed in which, after the base material is colored, a reversible thermosensitive recording layer is provided on the base material via an air layer (Japanese Patent Laid-Open No. 4-204). No. 220400) has a problem that the manufacturing method is complicated and the cost is high.

[0011]

As a result of intensive studies on the above problems, the present inventors have provided a reversible thermosensitive recording layer on one surface of a substrate and further on the other surface of the substrate. The present invention has been completed with the knowledge that the above problems can be solved by providing a colored layer.

The present invention is a reversible thermosensitive recording medium having a substrate, a reversible thermosensitive recording layer provided on one side of the substrate, and a colored layer provided on the other side of the substrate. Accordingly, the present invention provides a reversible thermosensitive recording medium in which the reversible thermosensitive recording layer contains an organic low molecular weight substance and a crosslinked resin matrix.

In a conventional recording medium having a metallic vapor deposition film having a specular gloss and a colored layer made of a color ink provided under the thermosensitive recording layer, the printing was difficult to see depending on the angle and the contrast was low. On the other hand, in the present invention, the reflected light from the base material also exists, and the angle dependence as in the past does not occur. Further, the number of manufacturing steps is smaller than in the conventional case, and the cost can be reduced.

Next, the recording medium of the present invention will be described more specifically.

FIG. 1 is a schematic sectional view of a recording medium of the present invention. In FIG. 1, a reversible thermosensitive recording medium 1 comprises a base material 2, a reversible thermosensitive recording layer 3 provided on one surface of the base material, and a colored layer provided on the other surface of the base material 2. It consists of 4.

As the substrate used in the present invention, a transparent plastic film such as polyethylene terephthalate and polypropylene is used, and the thickness is preferably 50 μm or more. This is because light is appropriately scattered in the transparent plastic film, so that the cloudy portion (recording portion) of the reversible thermosensitive recording layer can be seen more clearly, and when the thickness of the transparent plastic film is less than 50 μm, Such an effect cannot be obtained.

The reversible thermosensitive recording layer comprises a thermally crosslinked resin matrix containing an organic low molecular weight substance. The resin base material forms a layer in which an organic low molecular weight substance is uniformly dispersed and held, and greatly affects the transparency of the recording layer when transparent. Therefore, the resin base material is preferably a resin having high transparency, mechanical stability, and excellent film-forming property. Further, in the present invention,
In order to improve the heat resistance of the recording layer, the reversible thermosensitive recording layer is thermally crosslinked. Examples of the resin base material used for the heat-sensitive recording layer include vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-acrylic acid copolymer,
Vinyl chloride-vinyl acetate-maleic anhydride copolymer, vinyl chloride-vinyl acetate-hydroxyalkyl acrylate copolymer, epoxy-modified vinyl chloride-vinyl acetate copolymer, and other vinyl chloride-based copolymers; epoxy resin, phenoxy resin , A thermoplastic resin such as an acrylic resin, or another thermosetting resin. These resin base materials may be used alone or in combination of two or more kinds.

Examples of the cross-linking agent used for the heat cross-linking of the resin base material include amino resins such as hexamethoxymethyl melanin, benzoguanamine and urea resins, and 2,4-
/ 2,6-tolylene diisocyanate, isocyanates such as 4,4'-diphenylmethane diisocyanate, polymethylenediamine, diaminophenylmethane,
Diaminophenyl sulfone, o-toluidine, amines such as benzyldimethylamine, triglycidyl isocyanate, 3,4-epoxycyclohexylmethyl-
Examples thereof include epoxy compounds such as 3,4-epoxycyclohexanecarboxylate and epoxidized melamine resin. In addition, acid anhydride, methyl acrylic acid glycolate methyl ether, etc. may be used. Further, these cross-linking agents may be used together with a catalyst to accelerate the reaction.

The amount of the cross-linking agent to be added to the resin base material is 0.
It is 5 to 50% by weight, and particularly preferably 1.0 to 30% by weight. If the amount of the cross-linking agent is less than 0.5% by weight, the cross-linking is insufficient and the effect of preventing deterioration against repeated use is insufficient. On the other hand, if the amount is more than 50% by weight, the crosslinking agent acts like a plasticizer, and the white turbidity is lowered by repeated use, and finally sufficient contrast cannot be obtained, which is not preferable.

The organic low molecular weight compound used in the reversible thermosensitive recording medium of the present invention is composed of at least two components, and (A)
At least one compound selected from a higher fatty acid having 16 or more carbon atoms and a ketone having a melting point of 50 ° C. or more; and
(B) aliphatic saturated dicarboxylic acids, and the general _{formula: HOOC (CH 2) m -S-} (CH 2) n COOH least one selected from the sulfide (m and n are each an integer of 1 to 5) represented by Compounds of are preferably used.

Specific examples of such compounds used in the present invention are given below.

Organic low molecular weight substance (A) As the organic low molecular weight substance (A), higher fatty acids having 16 or more carbon atoms and aliphatic ketone compounds having a melting point of 50 ° C. or more are used.

The aliphatic ketones and higher fatty acids having a melting point of 50 ° C. or higher which can be used in the present invention are listed below. Specific examples of higher fatty acids used in the present invention include palmitic acid, margaric acid, stearic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, behenic acid, lignoceric acid, pentacosanoic acid, cerotic acid, heptacosanoic acid, montanic acid, tria. Contanoic acid, nonacosanoic acid, melissic acid, 2-heptadecenoic acid, 2-hexadecenoic acid, trans-2-octadecenoic acid, cis-2-
Octadecanoic acid, trans-4-octadecenoic acid, trans-3-hexadecenoic acid, cis-6-octadecenoic acid, elaidic acid, bassenic acid, trans-gondoinic acid, erucic acid, brassic acid, brassic acid, ceracoleic acid, trans-ceracolein Acid, trans-8, trans-10-octadecadienoic acid, linoelaidic acid,
Examples thereof include α-eleostearic acid, β-eleostearic acid, pseudoeleostearic acid, and 12,20-heneicosadienoic acid.

Examples of ketones having a melting point of 50 ° C. or higher include the following. 1) dialkyl ketones formula _{CH 3 (CH 2) n-} 1 CO (CH 2) n-1 CH 3 n ≧ 8 2) methyl alkyl ketones general formula _{CH 3 CO (CH 2) n} -3 CH 3 n ≧ 17 3) Phenyl alkyl ketone General formula C ₆ H ₅ CO (CH ₂ ) _n-1 CH ₃ n ≧ 10 4) Macrocyclic ketone

Embedded image 5) Symmetrical α-diketone General formula RCOCOR R = C _n H _{2n + 1} n ≧ 7 6) General formula RCH (OH) COR R = C _n H _{2n + 1} n ≧ 7 7) Cyclic acyloin

Embedded image 8) Ketene dimer

Embedded image The melting point of the organic low molecular weight substance (A) used in the present invention is 50.
It is preferably at least ° C. If the melting point is less than 50 ° C., it becomes unstable at room temperature, and the energy value required for recording changes during storage. For this reason, the transparent energy region shifts, and erasing cannot be performed with a constant set energy, which is not preferable.

[0025]Organic low molecular weight substance (B)  The organic low molecular weight substance (B) is compatible with the resin base material.
A compound is used. Aliphatic compounds
Saturated dicarboxylic acid and general formula: HOOC (CH₂)_m-S- (CH₂)_nSulfide represented by COOH (m and n are each an integer of 1 to 5)
Is preferred.

Further, an aliphatic dicarboxylic acid [general formula HOOC
Specific examples of (CH ₂ ) _n-2 COOH] include the following compounds. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ n Material name n Material name ───────── ─────────────────────────── 2 oxalic acid 15 pentadecanedioic acid 3 malonic acid 16 hexadecanedioic acid 4 succinic acid 17 heptadecanedioic acid 5 glutaric acid 18 octadecanedioic acid 6 adipic acid 19 nonadecanedioic acid 7 pimelic acid 20 eicosanedioic acid 8 suberic acid 21 heneicosandioic acid 9 azelaic acid 22 docosanedioic acid 10 sebacic acid 23 tricosanedioic acid 11 undecanedioic acid 24 tetracosanedioic acid 12 dodecanoic acid 26 Hexacosanedioic acid 13 Tridecanedioic acid 30 Nonacosanedioic acid 14 Tetradecanedioic acid 34 Dotriacontanedioic acid ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━

Further, the general formula HOOC (CH ₂ ) _m --S-(C
Specific examples of the sulfide represented by H ₂ ) _n COOH (m and n are each an integer of 1 to 5) include (1,1′-dicarboxy) dimethyl sulfide and (2,2′-dicarboxy) diethylfide. [Thiodipropionic acid], (3,3'-dicarboxy) dipropyl sulfide, (1,2'-dicarboxy) methylethyl sulfide, (1,3'-dicarboxy) methylpropyl sulfide, (1,4 ′ -Dicarboxy) methyl butyl sulfide, (2,3′-dicarboxy) ethyl propyl sulfide, (2,4′-dicarboxy) ethyl butyl sulfide,
Examples thereof include (5,5′-dicarboxy) dipentylfide, and thiodipropionic acid is particularly preferable.

Organic low molecular weight substance (A) and organic low molecular weight substance (B)
The blending ratio (A: B) is 95: 5 to 5: 9 by weight.
The range of 5, preferably 90:10 to 30:70 is preferable, and the range of 85:15 to 50:50 is particularly preferable. Organic low molecular weight substances against organic low molecular weight substances (A)
If the blending ratio of (B) is too small, the transparentization temperature region of the reversible thermosensitive recording layer will not be expanded, and if it is too large, the contrast will be significantly lowered, which is not preferable.

The compounding ratio of the organic low molecular weight substance (A) to the resin base material is preferably 5 to 100 parts by weight based on 100 parts by weight of the resin base material. If the compounding ratio of the organic low molecular weight substance (A) is less than this, sufficient contrast cannot be obtained, and
If the amount is large, sufficient film-forming properties cannot be obtained, and both are not preferable.

The mixing ratio of the organic low molecular weight substance (B) to the resin base material is 0.5 to 50 with respect to 100 parts by weight of the resin base material.
Parts by weight are preferred. If the compounding ratio of the organic low molecular weight substance (B) is less than this, orientation cannot be imparted to the melt of the organic low molecular weight substance (A). On the other hand, if the amount is too large, the compatibility limit with the resin base material is exceeded, leading to a decrease in contrast, and sufficient film formability cannot be obtained.

Furthermore, the mixing ratio of the total amount of the organic low molecular weight substances (A) and (B) to the resin base material is preferably 10 to 150 parts by weight with respect to 100 parts by weight of the resin base material. If the mixing ratio of the total amount of the organic low molecular weight substance is less than this range, sufficient contrast cannot be obtained, and if it exceeds 150 parts by weight, the coating film strength becomes low and the low molecular weight substance is deposited on the surface, which is not preferable.

To form the heat-sensitive recording layer, generally, a solution in which two components of a resin base material and an organic low molecular weight substance are dissolved is prepared, or a resin which does not dissolve at least one organic low molecular weight substance is used. A base material solution is prepared, and an organic low-molecular substance is dispersed in the form of fine particles, and these are coated on a substrate and dried to form a heat-sensitive recording layer. Further, the resin base material is cured by thermal crosslinking under appropriate heat treatment conditions.

The solvent used for forming the heat-sensitive recording layer may be variously selected depending on the types of the base material and the organic low molecular weight substance, and for example, tetrahydrofuran, methyl ethyl ketone,
Methyl isobutyl ketone, chloroform, carbon tetrachloride,
Methanol, ethanol, toluene, benzene, etc. can be mentioned.

The thickness of the thermosensitive recording layer is usually 5 to 40 μm, and particularly preferably 10 to 30 μm. If it is thicker than this, the sensitivity is lowered and a temperature gradient is generated in the thickness direction, so that sufficient white turbidity cannot be obtained, which is not preferable. On the other hand, if it is thinner than this, the contrast decreases, which is not preferable.

The recording medium of the present invention may further contain a lubricant, an antistatic agent, a plasticizer, a dispersant, a stabilizer, a surfactant, an inorganic or organic filler and the like, if necessary.

If necessary, an overcoat layer may be provided on the heat-sensitive recording layer directly or through an undercoat layer for protecting the layer. The overcoat layer may be made of an organic material such as acryl-based, silicone-based, fluorine-based, urethane-based, or SiO ₂ , Si.
Inorganic substances such as O, MgO, ZnO, TiO ₂ , Al ₂ O ₃ and Ta ₂ O ₅ may be used.

The resin used for these overcoat layers may be any of thermosetting, electron beam curable and ultraviolet curable resins.

For forming the overcoat layer, conventionally known coating methods and vacuum thin film forming methods (vacuum vapor deposition method, etc.) are used.
Thickness is 0.1-5.0 μm, preferably 1.0-3.0 μm
And If the overcoat is thinner than this, the protective effect is not sufficient, and if it is thicker than this, the amount of energy required for recording is large, which is not preferable.

Further, in order to improve the durability of the reversible thermosensitive recording layer, an intermediate layer may be provided between the layer and the overcoat layer.

The intermediate layer may be made of a material such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, polyester, polyamide, polyacrylate, polymethacrylate, polystyrene, nitrocellulose, ethyl cellulose, polyvinyl alcohol and polyvinyl butyral. Plastic resin: Thermosetting resin such as polyimide-based and polyurethane-based resin: or photo-curable resin by ultraviolet ray, electron beam, etc. may be used. Also in this case, the thickness of the intermediate layer is preferably 0.1 to 5.0 μm, and particularly preferably 0.1 to 3.0 μm for the same reason as that of the overcoat layer.

As the coloring material for the coloring layer provided on the other surface of the base material, any material conventionally used in these fields can be used. For example, acrylic,
Examples include gravure inks, flexo inks, planographic inks in which pigments and dyes are dispersed in urethane-based, epoxy-based, vinyl chloride-based, cellulose-based binders and the like. The color of the colored layer can be selected appropriately from black, blue, red, green, brown and purple, and among them, a relatively dark color is preferable so as to increase the contrast.

Further, a magnetic material may be blended in the colored layer of the reversible thermosensitive recording medium of the present invention to serve also as a magnetic material layer to provide a magnetic card capable of reversible thermosensitive recording. In this case, if a reversible thermosensitive recording layer is provided on one surface of the substrate and a magnetic material layer is further provided on the other surface of the substrate, the color of the magnetic material (black
A magnetic card can be obtained in which cloudy characters are recorded with (brown) as the background color.

A conventionally known magnetic paint is used for such a colored layer. For example, magnetic iron oxide is used as the magnetic substance in the magnetic paint, and γ-Fe ₂ O ₃ is particularly preferable.

Further, various additives may be mixed in the colored layer, if necessary. Examples of the additive include a plasticizer, a lubricant, a dispersant, an antistatic agent and a cross-linking agent.

The reversible thermosensitive recording medium of the present invention can be used by being attached to an IC card or the like using an adhesive or the like in addition to a magnetic card. In this case, the reversible thermosensitive recording layer may be provided on either side of the card. Further, it may be the entire surface or a part of the card, and may be adhered to any part of the card. The card having such a reversible thermosensitive recording layer can be used in a wide range of fields such as highway cards, various prepaid cards used in department stores and supermarkets, JR orange cards, stored fair cards, commuter passes and ID cards.

FIG. 2 shows a schematic sectional view of the magnetic card of the present invention. In FIG. 2A, the magnetic card 10 includes a transparent base material 11, a reversible thermosensitive recording layer 12 provided on one surface of the base material, and an overcoat provided on the reversible thermosensitive recording layer. It has a coat layer 13, a white hiding layer 14 provided on the overcoat layer, and a printing layer 15 provided on the white hiding layer. Here, the print layer 15 is formed excluding the display area portion 19. Also, the magnetic card 10
Has a magnetic material layer 16 provided on the other surface of the transparent substrate 11 and also serving as a colored layer, and a concealing layer 17 provided on the surface of the magnetic material layer. Further, in FIG. 2B, unlike in FIG. 2A, the coloring layer and the magnetic material layer are provided separately. That is, the colored layer 18 is provided on the other surface of the transparent substrate 11, and the magnetic material layer 16 and the masking layer 17 are provided on the surface of the colored layer.

The paint used for the white hiding layer is T
Pigments such as iO ₂ , SiO ₂ , and Al ₂ O ₃ and binders such as vinyl chloride resin, urethane resin, epoxy resin, and acrylic resin, and if necessary, toluene, methyl ethyl ketone, cyclohexanone, ethyl acetate, xylene, etc. It is preferable that the solvent is mixed.

For forming the white hiding layer, conventionally known coating methods and printing methods such as screen printing, offset printing and gravure printing are used, and the dry thickness thereof is 0.1 to 10 μm.
Is preferred. If the thickness of the white hiding layer is smaller than this, it is not preferable because the color of the lower layer cannot be covered, and if it is thicker than this, curling or cracking is caused, which is not preferable either.

The coating material used for the concealing layer provided on the other surface of the printing layer and the base material is an organic type,
A conventionally known inorganic pigment (dye) and a binder such as vinyl chloride resin, urethane resin, epoxy resin, acrylic resin, and, if necessary, a solvent such as toluene, methyl ethyl ketone, cyclohexanone, ethyl acetate, xylene, etc. The compounded one is preferable. The same method as that for the white hiding layer may be used to form the printing layer and the hiding layer. The thickness of the printed layer after drying is 0.1
The range of -10 μm is preferable, and the hiding layer has a range of 0.1-0.1 μm.
It is preferably in the range of 20 μm.

For each of the above layers, a resin having thermoplasticity, light (including electron beam / ultraviolet rays, etc.) curability and thermosetting property may be used, but light or thermosetting resin is particularly preferred.

At the time of forming the magnetic card of the present invention, an adhesive layer for the purpose of improving the adhesiveness between the substrate, the reversible thermosensitive recording layer, the overcoat layer, the white hiding layer, the coloring layer and the magnetic material layer. May be provided respectively.

Next, the reversible thermosensitive recording medium of the present invention will be described more specifically with reference to examples. In the following, "parts" means "parts by weight".

[0053]

【Example】

[Example 1] A transparent polyethylene terephthalate film (hereinafter referred to as a PET film) having a thickness of 100 µm was used as a substrate, and a black ink (XGL-325 manufactured by Sakata Inx Co., Ltd.) was formed as a coloring layer on one surface of the film having a thickness of 10 µm.
It was coated with a wire bar so as to be m and dried.

Next, a reversible thermosensitive recording layer composition liquid having the following composition was applied to the other surface of the substrate so as to have a film thickness of 20 μm, dried and then aged at 60 ° C. for 24 hours to obtain a recording layer. Was thermally crosslinked. The total amount of organic low molecular weight substances (behenic acid + thiodipropionic acid) in the reversible thermosensitive recording layer and the resin base material (vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer) are mixed in the resin matrix. Material 10
The total amount of organic low molecular weight substances is 40 parts by weight with respect to 0 parts by weight.

Reversible thermosensitive recording layer composition behenic acid 7 parts thiodipropionic acid 3 parts vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer (TA2) 25 parts 1,3-pentadiene copolymer 2 Parts Isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Company, "Coronate L") 3 parts Tetrahydrofuran 120 parts Further thereon, as an overcoat layer, 50 parts of acrylic UV curable resin (BR-370 manufactured by Asahi Denka Co., Ltd.) and methanol. Dry the coating solution consisting of 50 parts to a thickness of 2μ
It was coated so as to have a thickness of m and was cured by irradiation with ultraviolet rays of 500 mJ / cm ² .

A line type thermal head (8 dot / mm, printing energy: 0.6 mJ /
dot) was used for printing, and the contrast and visibility were examined. The contrast is Macbeth densitometer (Model RD-9
In 20), the difference in optical reflection density between the printed portion and the non-printed portion is shown. The angle dependence was observed from various angles under a fluorescent lamp, and the legibility of the recorded characters was visually evaluated. Furthermore, the visibility was evaluated by visually observing the overall visibility, taking into consideration both the contrast and the angle dependency.

Example 2 A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that a transparent PET film having a thickness of 188 μm was used as the substrate.

[Example 3] A reversible film was prepared in the same manner as in Example 1 except that a transparent PET film having a thickness of 188 µm was used as a base material, and the following magnetic material was applied as a coloring layer to a thickness of 15 µm after drying. A thermosensitive recording medium was prepared and evaluated.

Magnetic material (colored layer composition) γ-Fe ₂ O ₃ 40 parts Vinyl chloride-vinyl acetate-polyvinyl alcohol copolymer 20 parts Saturated polyester resin (manufactured by Toyobo Co., Ltd., "Byron 103") 5 parts Polyurethane elastomer (Japan Polyurethane Co., Ltd.) 7 parts Oleic acid 5 parts Toluene 60 parts Methyl isobutyl ketone 60 parts Isocyanate crosslinking agent (Nippon Polyurethane Company, "Coronate HL") 5 parts Triethylenediamine 0.5 parts [Example 4] Reversible thermosensitive recording A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the layer thickness was 10 μm.

[Example 5] The film thickness of the reversible thermosensitive recording layer was set to 3
A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the thickness was 0 μm.

[Example 6] A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the reversible thermosensitive recording layer was prepared by the following composition. The total amount of organic low molecular weight substances (behenic acid + thiodipropionic acid) in the reversible thermosensitive recording layer and the resin base material (vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer) are mixed in the resin matrix. The total amount of organic low molecular weight substances is 140 with respect to 100 parts by weight of the material.
Parts by weight. Reversible thermosensitive recording layer composition Behenic acid 24.5 parts Thiodipropionic acid 10.6 parts Vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer (TA2) 25 parts 1,3-pentadiene copolymer 2 parts Isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Company, "Coronate L") 3 parts Tetrahydrofuran 195 parts

[Example 7] A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the reversible thermosensitive recording layer was prepared by the following composition. The total amount of organic low molecular weight substances (behenic acid + thiodipropionic acid) in the reversible thermosensitive recording layer and the resin base material (vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer) are mixed in the resin matrix. The material was 100 parts by weight, and the total amount of the organic low molecular weight substances was 80 parts by weight. Reversible thermosensitive recording layer composition Behenic acid 14 parts Thiodipropionic acid 6 parts Vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer (TA2) 25 parts 1,3-pentadiene copolymer 2 parts Isocyanate system Crosslinking agent (Nippon Polyurethane Co., "Coronate L") 3 parts Tetrahydrofuran 150 parts

[Example 8] Hiding layer composition Aluminum powder 30 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 50 parts Methyl ethyl ketone 200 parts Toluene 50 parts As shown in FIG. The surface of the magnetic material layer 36 of the reversible thermosensitive recording medium was coated with the solution having the above composition by a roll coater. This was dried at 100 ° C. for 2 minutes to provide a hiding layer 37 having a thickness of 10 μm. on the other hand,
UV curable white ink is applied and printed on a portion except the display area 30 on the overcoat layer 33 side by using an offset printing machine, and then UV irradiation (irradiation energy: 50
0 mJ / cm ³ ) to provide the white hiding layer 34. Further, a printing layer 35 is provided on the surface of the white hiding layer 34 excluding the display area 30 with a four-color offset printing machine using four colors of ultraviolet curable ink (red, blue, yellow, black), and the magnetic card 20 Got The produced magnetic card was evaluated in the same manner as in Example 1, and good results were obtained.

[Comparative Example 1] A PET film having a thickness of 100 μm was used as a base material, and an aluminum vapor deposition film (50
(0 Å thickness) to form a metal reflective film, and then the same reversible thermosensitive recording layer as in Example 1 was formed thereon, and a reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1. .

[Comparative Example 2] A PET film having a thickness of 100 µm was used as a substrate, a colored layer similar to that of Example 1 was formed on one surface thereof, and then the same reversible thermosensitive recording as that of Example 1 was formed thereon. A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the layer was formed.

[Comparative Example 3] As a base material, P having a thickness of 25 μm was used.
A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the ET film was used.

[Comparative Example 4] The film thickness of the reversible thermosensitive recording layer was set to 7
A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the thickness was set to μm.

[Comparative Example 5] The film thickness of the reversible thermosensitive recording layer was set to 4
A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the thickness was 0 μm.

[Comparative Example 6] A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the reversible thermosensitive recording layer was prepared in the following composition. The total amount of organic low molecular weight substances (behenic acid + thiodipropionic acid) in the reversible thermosensitive recording layer and the resin base material (vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer) are mixed in the resin matrix. The total amount of low molecular weight organic materials is 180
It was made into a weight part. Reversible thermosensitive recording layer composition Behenic acid 31.5 parts Thiodipropionic acid 13.5 parts Vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer (TA2) 25 parts 1,3-pentadiene copolymer 2 parts Isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Company, "Coronate L") 3 parts Tetrahydrofuran 225 parts

[Comparative Example 7] A reversible thermosensitive recording medium was prepared and evaluated in the same manner as in Example 1 except that the reversible thermosensitive recording layer was adjusted to the following composition. The total amount of organic low molecular weight substances (behenic acid + thiodipropionic acid) in the reversible thermosensitive recording layer and the resin base material (vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer) are mixed in the resin matrix. The amount of the material was 100 parts by weight, and the total amount of the organic low molecular weight substances was 8 parts by weight. Reversible thermosensitive recording layer composition Behenic acid 1.4 parts Thiodipropionic acid 0.6 parts Vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer (TA2) 25 parts 1,3-pentadiene copolymer 2 parts Isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Company, "Coronate L") 3 parts Tetrahydrofuran 96 parts

The above results are shown in Table 1.

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Contrast angle dependence visibility ─── ─────────────────────────────── Example 1 0.80 None ○ Example 2 0.85 None ◎ Example 3 1.00 None ◎ Example 4 0.75 None ○ Example 5 1.20 None ◎ Example 6 1.02 None ◎ Example 7 0.93 None ◎ ────────────── ─────────────────── Comparative Example 1 0.90 Yes × Comparative Example 2 0.60 None △ Comparative Example 3 0.65 None △ Comparative Example 4 0.50 None × Comparative Example 5 0.55 None △ Comparative Example 6 0.61 None △ Comparative Example 7 0.29 None × ━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━

[Comparative Example 8] As a comparative example in the case where the reversible thermosensitive recording layer was not thermally crosslinked, the reversible thermosensitive recording layer was formed in the same manner as in Example 1 except that the reversible thermosensitive recording layer was formed by the following formulation (without a crosslinking agent). A thermosensitive recording medium was prepared.

[0074]Reversible thermosensitive recording layer composition (no crosslinking agent)  Behenic acid 7 parts Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer (UCC, VYHH) 25 parts 1,3-pentadiene polymer 2 parts Tetrahydrofuran 120 parts The sample of Comparative Example 8 and Example 1 Regarding the sample
Durability when repeatedly printed / erased in the same place
Was evaluated. Energy of thermal head used for evaluation
Is 0.6mJ / dot, and erase is stamped at 80 ℃
Was contacted for 1 second. The results are shown in Fig. 4.

The vertical axis in FIG. 4 represents the optical reflection density measured by a Macbeth densitometer (model RD-920), and the horizontal axis represents the number of repetitions. On the vertical axis, the higher the value, the higher the transparency, and the lower the value, the higher the white turbidity.

[0076]

The reversible thermosensitive recording medium of the present invention has a higher contrast than the conventional one and the visibility is greatly improved. When the reversible thermosensitive recording layer is thermally crosslinked, the heat resistance strength is improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a specific example of a reversible thermosensitive recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view of a specific example of a magnetic card of the present invention.

3A and 3B are a plan view and a cross-sectional view of a magnetic card manufactured in Example 8.

FIG. 4 is a graph showing changes in optical reflection density due to repeated printing / erasing of a reversible thermosensitive recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reversible thermosensitive recording medium 2 Base material 3 Reversible thermosensitive recording layer 4 Colored layer 10 Magnetic card 11 Base material 12 Reversible thermosensitive recording layer 13 Overcoat layer 14 White hiding layer 15 Printing layer 16 Magnetic material layer 17 Hiding layer 18 Coloring Layer 19 Display Area 20 Magnetic Card 30 Display Area 31 Base Material 32 Reversible Thermosensitive Recording Layer 33 Overcoat Layer 34 White Hiding Layer 35 Printing Layer 36 Magnetic Material Layer 37 Hiding Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06K 19/06 G06K 19/00 B

Claims (7)

[Claims] 1. A reversible thermosensitive recording material having a transparent substrate, a reversible thermosensitive recording layer provided on one surface of the substrate, and a colored layer provided on the other surface of the substrate. There
A reversible thermosensitive recording medium, wherein the reversible thermosensitive recording layer comprises an organic low molecular weight substance and a crosslinked resin matrix. 2. The reversible thermosensitive recording layer comprises an organic low molecular weight substance in an amount of 10 to 1 with respect to 100 parts by weight of a crosslinked resin base material.
The reversible thermosensitive recording medium according to claim 1, comprising 50 parts by weight. 3. The organic low molecular weight compound (A) has 1 carbon atom.
At least one compound selected from 6 or more higher fatty acids and a ketone having a melting point of 50 ° C. or higher, and (B) an aliphatic saturated dicarboxylic acid and a general formula: HOOC (CH ₂ ) _m —S— (CH ₂ ) _n A compounding ratio of the organic low molecular weight compound (A) and the organic low molecular weight compound (B) containing at least one compound selected from sulfides represented by COOH (m and n are each an integer of 1 to 5) ( The reversible thermosensitive recording medium according to claim 1 or 2, wherein A: B) is 85:15 to 50:50. 4. The reversible thermosensitive recording medium according to claim 1, wherein the colored layer contains a magnetic material. 5. The reversible thermosensitive recording medium according to claim 1, wherein the base material is a transparent plastic having a thickness of 50 μm or more. 6. The reversible thermosensitive recording layer has a thickness of 10 to 30 μm.
The reversible thermosensitive recording medium according to claim 1, wherein m is m. 7. A reversible thermosensitive recording layer, an overcoat layer, a white hiding layer and a printing layer are sequentially provided on one surface of the substrate, and the other surface of the substrate is sequentially A magnetic card provided with a magnetic material layer and a masking layer.